Local Earthquake Tomography in the Central Alboz-Iran to Determining Upper Crust Velocity Anomaly

Abstract

Seismic inversion for three-dimensional variations of velocity is often used to delineate velocity anomalies including magma bodies in the crust and upper mantle. A 3-D Vp and Vs model is obtained for the upper crust in the Central Alborz Mountains using the local travel-time earthquake tomography method. About 350 seismic events distributed around Alborz Mountain Ranges from surface down to a depth of about 30 km have been used to elucidate the P and S wave velocity structure. The seismic arrival times are directly inverted using a 1D velocity model as the starting model in the inversion. The simultaneous inversion of hypocentral and velocity model parameters had a remarkable impact on improving the location of the earthquakes. The optimal gridding and regularization parameters are estimated via synthetic modeling. Tomography results show considerable velocity anomaly in Damavand cone nearby the region. Both the P- and S-wave velocities are reduced compared to the surrounding below 10 km depth.